Understanding how the stem cells of the colonic mucosa self-renew and give rise to a diversity of cell types is a major problem in gastrointestinal research. The overall aim of this project is to characterize the stem cell of the colonic mucosa. We will identify the factors that control the growth and differentiation of these cells and identify unique gene expression profiles that will allow us to identify these cells. We have developed a method for preparing a viable single cell suspension from the colonic mucosa. This has allowed us to use a novel clonogenic assay to search for the factors that control the growth and differentiation of the colonic stem cells. We are also using a novel crypt dissection technique to prepare crypt fragments from which we isolate RNA. We are using this RNA to do comparative microarray studies. This technique allows us to identify the genes that are uniquely expressed in the different crypt compartments. We have found that there are a number of unknown genes that are only expressed in the proliferative compartment of the crypt. We are currently attempting to identify these genes and will determine if these are unique markers for the colonic stem cell. The identification of growth factors for the cells of the colonic mucosa may prove to be useful in enhancing the recovery of this tissue after damage such as following chemotherapy. The identification of unique markers for the colonic stem cell will allow us to enrich for this cell population and undertake transplantation studies.